Use class length for random TryteString generation

iota/crypto/types.py

@@ -112,6 +112,11 @@ class Seed(TryteString):
     - https://iota.stackexchange.com/q/249
     """
 
+    LEN = 81
+    """
+    Length of a Seed.
+    """
+
     def __init__(self, trytes=None):
         # type: (Optional[TrytesCompatible]) -> None
         if trytes and len(trytes) > Hash.LEN:

iota/types.py

@@ -68,19 +68,28 @@ class TryteString(JsonSerializable):
     """
 
     @classmethod
-    def random(cls, length):
-        # type: (int) -> TryteString
+    def random(cls, length=None):
+        # type: (Optional[int]) -> TryteString
         """
         Generates a random sequence of trytes.
 
-        :param int length:
+        :param Optional[int] length:
             Number of trytes to generate.
 
         :return:
             :py:class:`TryteString` object.
         """
         alphabet = list(itervalues(AsciiTrytesCodec.alphabet))
         generator = SystemRandom()
+        try:
+            if length is None:
+                length = cls.LEN
+
+            if length <= 0:
+                raise TypeError("length parameter needs to be greater than zero")
+        except AttributeError:  # class has no LEN attribute
+            if length is None:
+                raise TypeError("{class_name} does not define a length property".format(class_name=cls.__name__))
 
         # :py:meth:`SystemRandom.choices` wasn't added until Python 3.6;
         # for compatibility, we will continue to use ``choice`` in a

test/crypto/types_test.py

@@ -79,6 +79,12 @@ def test_init_error_too_short(self):
     with self.assertRaises(ValueError):
       Digest(b'9' * (2 * Hash.LEN - 1))
 
+  def test_random(self):
+    """
+    Generating a random Digest should fail.
+    """
+    with self.assertRaises(TypeError):
+      random_digest = Digest.random()
 
 # noinspection SpellCheckingInspection
 class PrivateKeyTestCase(TestCase):
@@ -152,3 +158,10 @@ def test_get_digest_multiple_fragments(self):
     #
     # Each fragment is processed independently, which is critical for
     # multisig to work correctly.
+
+  def test_random(self):
+    """
+    Generating a random PrivateKey should fail.
+    """
+    with self.assertRaises(TypeError):
+      random_digest = PrivateKey.random()

test/transaction/types_test.py

@@ -6,7 +6,8 @@
 
 from six import binary_type
 
-from iota import TransactionHash
+from iota import TransactionHash, BundleHash, Fragment, TransactionTrytes, \
+  Nonce
 
 
 class TransactionHashTestCase(TestCase):
@@ -39,3 +40,42 @@ def test_init_error_too_long(self):
         b'JVMTDGDPDFYHMZPMWEKKANBQSLSDTIIHAYQUMZOK'
         b'HXXXGJHJDQPOMDOMNRDKYCZRUFZROZDADTHZC99999'
       )
+
+  def test_random(self):
+    """
+    Creating a random TransactionHash object.
+    """
+    random_tx_hash = TransactionHash.random()
+    self.assertEqual(len(random_tx_hash), TransactionHash.LEN)
+
+class BundleHashTestCase(TestCase):
+  def test_random(self):
+    """
+    Creating a random BundleHash object.
+    """
+    random_bundle_hash = BundleHash.random()
+    self.assertEqual(len(random_bundle_hash), BundleHash.LEN)
+
+class FragmentTestCase(TestCase):
+  def test_random(self):
+    """
+    Creating a random Fragment object.
+    """
+    random_fragment = Fragment.random()
+    self.assertEqual(len(random_fragment), Fragment.LEN)
+
+class TransactionTrytesTestCase(TestCase):
+  def test_random(self):
+    """
+    Creating a random TransactionTrytes object.
+    """
+    random_tx_trytes = TransactionTrytes.random()
+    self.assertEqual(len(random_tx_trytes), TransactionTrytes.LEN)
+
+class NonceTestCase(TestCase):
+  def test_random(self):
+    """
+    Creating a random Nonce object.
+    """
+    random_nonce = Nonce.random()
+    self.assertEqual(len(random_nonce), Nonce.LEN)

test/types_test.py

@@ -754,6 +754,20 @@ def test_random(self):
     # generated.
     self.assertEqual(len(trytes), Hash.LEN)
 
+  def test_random_no_length(self):
+    """
+    Trying to create a random TryteString without specifying length.
+    """
+    with self.assertRaises(TypeError):
+      trytes = TryteString.random()
+
+  def test_random_wrong_length(self):
+    """
+    Generating random Trytestring with negative length.
+    """
+    with self.assertRaises(TypeError):
+      trytes = TryteString.random(length=-5)
+
   def test_from_bytes(self):
     """
     Converting a sequence of bytes into a TryteString.
@@ -883,6 +897,14 @@ def test_from_trits_wrong_length_padded(self):
       b'RBTC',
     )
 
+class HashTestCase(TestCase):
+  def test_random(self):
+    """
+    Generating a random Hash.
+    """
+    rand = Hash.random()
+    self.assertEqual(len(rand), Hash.LEN)
+
 
 # noinspection SpellCheckingInspection
 class AddressTestCase(TestCase):
@@ -1124,6 +1146,12 @@ def test_remove_checksum_second_time(self):
     self.assertFalse(addy.is_checksum_valid())
     self.assertTrue(len(addy) == Address.LEN)
 
+  def test_random(self):
+    """
+    Creating a random Address object.
+    """
+    addy = Address.random()
+    self.assertEqual(len(addy), Address.LEN)
 
 # noinspection SpellCheckingInspection
 class AddressChecksumTestCase(TestCase):
@@ -1149,6 +1177,13 @@ def test_init_error_too_long(self):
       # If it's an address checksum, it must be 9 trytes exactly.
       AddressChecksum(b'FOXM9MUBX9')
 
+  def test_random(self):
+    """
+    Creating a random AddressChecksum object.
+    """
+    checksum = AddressChecksum.random()
+    self.assertEqual(len(checksum), AddressChecksum.LEN)
+
 
 # noinspection SpellCheckingInspection
 class TagTestCase(TestCase):
@@ -1167,3 +1202,10 @@ def test_init_error_too_long(self):
     with self.assertRaises(ValueError):
       # 28 chars = no va.
       Tag(b'COLOREDCOINS9999999999999999')
+
+  def test_random(self):
+    """
+    Creating a random Tag object.
+    """
+    tag = Tag.random()
+    self.assertEqual(len(tag), Tag.LEN)